This invention relates to a process for decaffeinating aqueous liquids of vegetable origin. The invention is described with particular emphasis on the decaffeination of coffee extract, however decaffeination of other caffeine-containing aqueous liquids, such as tea, mate and the like, may be possible.
Current commercial decaffeination of coffee is effected by the removal of caffeine from whole, green coffee beans. The beans are first moistened and then extracted with a solvent which is relatively specific for caffeine. Typically the solvent may be either a chlorinated hydrocarbon sclvent, such as discussed in U.S. Pat. No. 3,700,465, or a caffeine-deficient water solution of coffee solubles, such as disclosed in U.S. Pat. No. 2,309,092. The processes described in these two patents, herein incorporated by reference, are well-known in the art.
Decaffeination of an aqueous extract obtained from roasted coffee beans by directly contacting the extract with a chlorinated solvent is also known in the coffee art, as disclosed in U.S. Pat. No. 2,933,395. The decaffeinated aqueous extract would then typically be dried, such as by spray-drying or freeze-drying, in order to obtain a decaffeinated soluble coffee.
Coffee beans or extract decaffeinated in accordance with above-described processes have been found to undergo changes which are readily detectable when one compares the taste of coffee beverages produced from decaffeinated coffee beans or extract with their caffeinated couterparts. Additionally, the decaffeinated coffee beans or extract which has been contacted either directly or indirectly with a hydrocarbon solvent undesirably retain a small amount of the solvent.
Thus the coffee industry has sought alternative systems for decaffeination which will minimize or eliminate the above problems. U.S. Pat. No. 3,749,584 to Kurtzman et al. has disclosed a mold, Penicillium crustosum, for the biological decaffeination of coffee; however the procedure of this patent which uses intact mold organisms as the caffeine metabolizing agent with the subsequent removal of these cells from the liquid or beverage is not seen to be acceptable for the commercial preparation of coffee products. Separation of the live cells from the decaffeinated liquid would likely be an expensive and/or lengthy operation, since all or substantially all of the cells would have to be removed to produce a commercially acceptable product. Binding of intact organisms into an insoluble support would be one means of eliminating the separation step and increasing the practicality of such an intact organism process. However, the use of the intact mold organisms may produce off-flavors within the coffee extract since chemical changes other than decaffeination could be produced by the organisms.